The number of cellular phone services has substantially increased world-wide and, as it has, the world-wide demand for antennas having the capacity for receiving such wireless services has also increased. This increased demand has typically been met by reflector, or xe2x80x9cdish,xe2x80x9d antennas, which are well known in the art. Reflector antennas are commonly used in cellular environments for receiving telephone services, such as the transmission and reception of cellular phone signals from a moving vehicle. However, reflector antennas have several drawbacks. For example, they are bulky and relatively expensive for residential use. Furthermore, inherent in reflector antennas are feed spillover and aperture blockage by a feed assembly, which significantly reduces the aperture efficiency of a reflector antenna, typically resulting in an aperture efficiency of only about 55%.
An alternative antenna, such as a microstrip antenna, overcomes many of the disadvantages associated with reflector antennas. Microstrip antennas, for example, require less space, are simpler and less expensive to manufacture, and are more compatible with printed-circuit technology than reflector antennas. Microstrip array antennas, i.e., microstrip antennas having an array of microstrips, may be used with applications requiring high directivity. Microstrip array antennas, however, typically rely on traveling waves and require a complex microstrip feed network, which contributes significant power loss to the overall antenna loss.
What is needed, then, is a low-cost, compact antenna having a high aperture efficiency, and which does not require a complex feed network.
The present invention, accordingly, provides for a low-cost, compact antenna having a high aperture efficiency. To this end, a cylindrical, double-layer microstrip antenna of the present invention includes first and second cylindrically-shaped dielectric layers having first sides secured together with an array of conducting strips conformally interposed therebetween, the strips being spaced to define a slot between each pair of adjacent strips. A conductive ground plane is disposed on an interior second side of the first dielectric layer, and an array of spaced apart radiating patches are conformally disposed on an exterior second side of the second dielectric layer, each of which patches is positioned over a corresponding slot. Responsive to electromagnetic energy, a high-order standing wave is induced in the antenna and a directed beam is transmitted from and/or received into the antenna.